Jab in the dark: Why we don’t have a universal flu vaccine

Egg testing at Sinovac Biotech, during the production of an H1N1 vaccine

Reuters/China Daily

By Debora MacKenzie

Why isn’t the flu vaccine better?

Nearly all flu vaccines are made of viruses grown in hens’ eggs, a process dating from the 1940s that takes between six and eight months. One egg is inoculated with a flu virus that grows well in eggs and has been equipped with the H and N proteins from a virus strain thought likely to circulate next winter. The world has the capacity to make 1.5 billion doses of vaccine each protecting against three or four strains, and so each requiring three to four eggs. Vaccines this year contain both the circulating A strains, and one or both of the Bs. Actual production varies with predicted demand.

This process means virologists must predict months in advance which viruses will circulate so companies can grow the right vaccines. Sometimes they get it wrong, although this year the vaccine virus was a good match, says Ian Barr of the University of Melbourne.

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There is still a problem, though. A review last year found that the main, injected vaccine, made of killed viruses, protected only 33 per cent of recipients against H3N2 – which is the dominant strain this year. This fell to 24 per cent in the over-65s. In the Australian winter just past, the vaccine protected only 10 per cent of recipients of any age from H3N2, and made no difference in elderly people, although it worked …